Glass base material producing device

ABSTRACT

A glass base material manufacturing apparatus for manufacturing a glass base material comprising: a plurality burners, arranged in a row at a predetermined intervals along the longitudinal direction of a starting base material of the glass base material, for forming a deposit, which is a base material of the glass base material by depositing glass soot on the starting base material while moving reciprocatory over a section of the entire length of the starting base material along the longitudinal direction of the starting base material; a plurality of flow rate regulators, at least one of which is connected to the plurality of burners, respectively, for regulating a flow rate of raw material gas of the glass soot, which is supplied to the plurality of burners; and a control unit connected to each of the plurality of flow rate regulators for controlling individually the plurality of flow rate regulators.

This is the U.S. national stage of PCT/JP01/06271 filed on Jul. 18,2001, further of a Japanese patent application, 2000-230508 filed onJul. 31, 2000, 2000-234108 filed on Aug. 2, 2000, 2000-238502 filed onAug. 7, 2000, the contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present embodiment relates to a glass base manufacturing apparatusand method thereof. More particularly, the present embodiment relates toa glass base manufacturing apparatus and method thereof formanufacturing a glass base material, which is a base material of anoptical fiber.

2. Description of the Related Art

FIG. 1 shows the configuration of a conventional glass base materialmanufacturing apparatus. A glass base material manufacturing apparatushas a chuck 12 and burners 22A–22D. A chuck 12 hold the both ends of thestarting base material 2. Furthermore, a chuck 12 rotates the startingbase material 2 around the axis of the starting base material 2. Theburners 22A–22D are arranged at equal intervals in the row along thelongitudinal direction of the starting base material 2. Raw materialgas, fuel gas, and assist combustion gas are supplied to the burners22A–22D. The burners 22A–22D hydrolyze the supplied raw material gaswhile moving reciprocatory along the longitudinal direction of thestarting base material 2 and ejecting glass soot to the starting basematerial 2. The deposit 10 is formed by depositing glass soot around thestarting base material 2 with the burners 22A–22D.

The glass base material used as base material of an optical fiber ismanufactured by heat-treating and vitrifying the glass soot deposited onthe circumference of the starting base material 2. An optical fiberpreform is obtained by elongating and reducing the diameter of a glassbase material to the form suitable for drawing, and an optical fiber ismanufactured by drawing the glass base material.

FIG. 2 shows a deposit amount of the glass soot by the burners 22A–22Daccording to a full-range traverse method. In the case of the full-rangetraverse method, all the burners 22A–22D move reciprocatory from one endof a region, on which glass soot is deposited, to another end of theregion while moving beyond an effective part, which can be effectivelyused as a glass base material product. Furthermore, each burner 22A–22Ddeposits glass soot for a specific deposit amount at uniform thicknesswithin the range of the effective part. Therefore, the whole thicknessof the deposited glass soot becomes substantially uniform along themoving direction of the burners 22A–22D even when the deposited amountof the glass soot of each burner 22A–22D is different, respectively.

FIG. 3 shows a deposited amount of the glass soot by the burners 22A–22Faccording to the partial traverse method. In the case of the partialtraverse method, the burners 22A–22F deposit glass soot on the startingbase material 2 while moving reciprocatory over a part of the section ofthe whole length of the starting base material 2. For example, thestarting position of the reciprocate movement of each of the burners22A–22F is shifted partially and sequentially, and glass soot isdeposited on the starting base material 2 (as referred to in JapanesePatent Application Laid-Open No. 3-228845).

Since the partial traverse method can increase the number of the burnerswithout increasing the unnecessary part, which cannot be used as a glassbase material product, as compared with the full-range traverse methodas shown in FIG. 2, the partial traverse method can increase the speedfor depositing glass.

However, in case of the partial traverse method, each burner 22A–22Fmoves reciprocatory a part of sections of the whole length of theeffective part. Therefore, as shown in FIG. 3, when the deposited amountof glass soot is different for each of the burners, the whole thicknessof the deposited glass soot becomes uneven along the longitudinaldirection of the effective part.

If the deposited amount of the glass soot along the longitudinaldirection of the starting base material 2 is not uniform, the glass basematerial, which is generated by vitrifying the deposit 10, has a clad,which is deposited around a core, having a varied thickness.

Therefore, if a preform is manufactured by elongating and reducing thediameter of a glass base material having a clad, the thickness of whichis not uniform, and an optical fiber, which is the final product, ismanufactured by drawing the preform, the diameter of the core of theoptical fiber will fluctuate. Since light propagates inside a core, ifthe core diameter is changed, a predetermined characteristic requiredfor an optical fiber cannot be acquired. Therefore, when the depositedamount of glass soot is uneven along the longitudinal direction of theeffective part, the process for grinding the part, where the thicknessof the deposited amount is large, to make the thickness to be uniformbecomes necessary, and the manufacturing cost thus increases.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present embodiment to provide a glassbase manufacturing apparatus and method thereof which overcomes theabove issues in the related art. This object is achieved by combinationsdescribed in the independent claims. The dependent claims define furtheradvantageous and exemplary combinations of the present embodiment.

According to the first aspect of the present embodiment, a glass basematerial manufacturing apparatus for manufacturing a glass basematerial, which is used as a base material of an optical fiber,comprises: a plurality burners, arranged in a row at predeterminedintervals along the longitudinal direction of a starting base materialof the glass base material, for forming a deposit, which is a basematerial of the glass base material by depositing glass soot on thestarting base material while moving reciprocatory over a section of theentire length of the starting base material along the longitudinaldirection of the starting base material; a plurality of flow rateregulators, at least one of which is connected to the plurality ofburners, respectively, for regulating a flow rate of raw material gas ofthe glass soot, which is supplied to the plurality of burners; and acontrol unit connected to each of the plurality of flow rate regulatorsfor controlling individually the plurality of flow rate regulators.

The control unit may have: a first control unit which controls aplurality of the flow rate regulators so that the raw material gas of abase flow rate is supplied to the plurality of the burners; and a secondcontrol unit which controls each of the plurality of flow rateregulators according to a correction value of flow rate of the rawmaterial gas supplied to the burners, the correction value beingcalculated for each of the plurality of burners over the base flow rate.

The second control unit may calculate the correction value for each ofthe plurality of flow rate regulators based on a deposition ratio of theglass base material, which is formed by vitrifying the deposit actuallydeposited by the plurality of burners.

The second control unit may adjust the correction value for each of theplurality of flow rate regulators according to a ratio between adeposition ratio of first glass base material, which is formed byvitrifying the deposit formed by controlling the flow rate regulatorsusing the first control unit corresponding to each position of theplurality of burners, and a deposition ratio of second glass basematerial, which is formed by vitrifying the deposit formed bycontrolling the flow rate regulators using the first control unit andthe second control unit.

The control unit may be connected to a preform analyzer, which measuresthe outside diameter and the core diameter of the glass base material.The second control unit may calculate the correction value to be 50%less than the base flow rate. The first control unit may control theflow rate regulator so that an amount of the raw material gas suppliedto the burners is changed with the progress of time. The plurality offlow rate regulators may be connected to one of the burners. Theplurality of flow rate regulators may control different types of flowrate of the raw material gas, respectively.

The glass base material manufacturing apparatus may further comprise: afirst moving mechanism that moves the plurality of burners reciprocatoryin a first cycle along the longitudinal direction of the starting basematerial; and a second moving mechanism that moves the first movingmechanism reciprocatory in a second cycle, the cycle of the second cyclebeing longer than the first cycle.

The glass base material manufacturing apparatus may further comprise: areaction vessel which accommodates the plurality of burners; and adeformation reduction mechanism, which reduces a deformation of, thereaction vessel caused by heat generated when manufacturing the glassbase material. The deformation reduction mechanism may include aflexural structure part formed in the reaction vessel. The flexuralstructure part may be formed around the reaction vessel. The deformationreduction mechanism may include deformation restriction unit, whichrestricts deformation of the reaction vessel. The deformation reductionmechanism may include at least one of the deformation restriction unitsprovided around a circumference of the reaction vessel.

A material of the deformation restriction unit may be carbon steel orstainless steel. The material of the deformation restriction unit may bea steel pipe having a square cross section. The reaction vessel may havea wall, the surface of which is continuous flexural shape, as thedeformation reduction mechanism. The reaction vessel may have a slidepart, in which a part of a wall of the reaction vessel slides to beoverlapped with another part of the wall of there action vessel, as thedeformation reduction mechanism. The reaction vessel may have the slidepart around the circumference of the reaction vessel.

The glass base material manufacturing apparatus may further have aholding unit, which holds the deposit and transports the deposit outsidethe glass base material manufacturing apparatus; and the holding unithas a means to hold a conical part, which is formed on both ends of thedeposit. The holding unit may have a concave part, an angle of which issubstantially the same as an inclination of an angle of the conical partof the deposit. The concave part may be a curved groove. The concavepart may be a substantially V-shaped groove.

The holding unit may have a clamp, which includes a concave part thatholds the conical part by sandwiching the conical part from both of anupper side and a lower side of the conical part. The plurality of clampsmay be rotated around an axis, which couples the plurality of clampswith each other.

The holding unit may have a clamp including the concave part, whichholds the conical part by sandwiching the conical part; and a holdingangle adjustment unit for adjusting an angle of the concave part of theclamp to be substantially the same as an angle of an inclination of apart of the conical part. The holding angle adjustment unit may rotatethe clamp around a longitudinal direction of the clamp as an axis. Theholding unit may have a holding pressure adjustment unit for holding theconical part by substantially uniform pressure. The holding pressureadjustment unit may be an elastic body formed on a surface of the clampthat has contact with the conical part.

The holding pressure adjustment unit may have a plurality of columnarobjects each of which moves telescopically according to a curved surfaceof the conical part. The holding unit may have a mechanism for adjustinga position of the clamp in the axial direction of the deposit. Themechanism for adjusting the position of the clamp may have an arm thatsupports the clamp and screw shaft, which engages with the arm and movesthe arm in the axial direction of the deposit.

According to the second aspect of the present embodiment, a method formanufacturing a glass base material used as a base material of anoptical fiber, comprises: depositing glass soot on a starting basematerial of the glass base material by ejecting glass soot from aplurality of burners to the starting base material while moving theplurality of burners reciprocatory over a section of the entire lengthof the starting base material along the longitudinal direction of thestarting base material; and controlling f low rate of raw material gasof the glass soot supplied to the plurality of burners, individually foreach of the plurality of burners.

The method may further comprise: vitrifying a deposit of the glass sootdeposited to generate the glass base material; and the controlling maycontrol the flow rate of the raw material gas individually for each ofthe plurality of burners based on a deposition ratio of the glass basematerial generated by the vitrifying.

The depositing of glass soot may have a first batch depositing thatdeposits the glass soot on the starting base material to generate afirst batch of the deposit by supplying the raw material gas of a baseflow rate to the plurality of burners; and the vitrifying of deposit mayhave a first batch vitrifying that vitrifies the first batch of thedeposit to generate a first batch of the glass base material; andcalculating a correction value of a flow rate of the raw material gas,which is supplied to the burners, over the base flowrate for each of theplurality of burners based on the deposition ratio of the first batch ofthe glass base material generated by the first batch vitrifying.

The depositing of glass soot may further have a second batch depositingthat generates a second batch of the deposit by depositing the glasssoot on the starting base material by supplying the raw material gas toeach of the plurality of burners, respectively according to a correctionvalue, which is obtained by correcting the correction value calculatedby calculating over the base flow rate.

The controlling of flow rate may have first batch controlling thatcontrols a flow rate of the raw material gas to supply the raw materialgas of the base flow rate to the plurality of burners on the first batchdepositing; and second batch controlling that controls a flow rate ofthe raw material gas supplied to each of the plurality of burnersindividually according to a value, which is obtained by correcting thecorrection value over the base flow rate, on the second batchdepositing.

The calculating may calculate the correction value for each of theplurality of burners based on a deposition ratio of the first batch ofthe glass base material generated by the first batch vitrifying.

The vitrifying of deposit may further have a second batch vitrifyingthat vitrifies the second batch of the deposit generated by the secondbatch depositing to generate a second batch of the glass base material;and the method may further comprise: calculating the correction valuefor each of the plurality of burners based on a ratio between adeposition ratio of the first batch of the glass base material generatedby the first batch vitrifying corresponding to each position of theplurality of burners and a deposition ratio of the second batch of theglass base material generated by the second batch vitrifying.

The depositing of glass soot may further have a third batch depositingthat generates a third batch of the deposit by depositing the glass sooton the starting base material by supplying the raw material gas to eachof the plurality of burners based on a value obtained by correcting thecorrection value calculated by the calculating over the base flow rate;and the controlling may further have a third batch controlling thatindividually controls the flow rate of the raw material gas supplied toeach of the plurality of burners based on a value obtained by correctingthe calculated correction value over the base flow rate; and thevitrifying may further have a third batch vitrifying that vitrifies thethird batch of the deposit generated by the third batch depositing togenerate a third batch of the glass base material.

The calculating may calculate the correction value to be 50% or less ofthe base flow rate. The first batch controlling may control the flowrate of the raw material gas supplied to the burners to be changed withthe progress of time. The first batch depositing and second batchdepositing may supply a plurality type of the raw material gas to one ofthe burners; and the first batch controlling and the second batchcontrolling may control individually each flow rate of the pluralitytypes of the raw material gas. The method may further comprise: holdingthe glass base material; and the holding may hold a conical part formedon both ends of the glass base material.

This summary of the invention does not necessarily describe all thenecessary features of the present embodiment. The present embodiment mayalso be a sub-combination of the above described features. The above andother features and advantages of the present embodiment will become moreapparent from the following description of embodiments taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the configuration of a conventional glass base materialmanufacturing apparatus.

FIG. 2 shows a deposit amount of the glass soot by the burners 22A–22Daccording to a full-range traverse method.

FIG. 3 shows a deposited amount of the glass soot by the burners 22A–22Faccording to the partial traverse method.

FIG. 4 shows an example of the glass base material manufacturingapparatus 200 of the present embodiment.

FIG. 5 shows the trajectory of the burner 22A by the reciprocatorymovement of the burner 22A.

FIG. 6 shows a process for manufacturing the glass base material usingthe glass base material manufacturing apparatus 200 shown in FIG. 4.

FIG. 7 shows the change of each deposition ratio of Example 1 andExample 2.

FIG. 8 shows the rate of change of the deposition ratio of Example 1 andthe deposition ratio of Example 2.

FIG. 9 shows the change of deposition ratio in Example 3 and Example 1.

FIG. 10 shows the rate of change between the deposition ratio of Example3 and the deposition ratio of Example 1.

FIG. 11 shows an embodiment of the deformation reduction mechanism ofthe glass base material manufacturing apparatus 200.

FIG. 12 shows other embodiments of a deformation reduction mechanism.

FIG. 13 shows another embodiment of a deformation reduction mechanism.

FIG. 14 shows other embodiments of a deformation reduction mechanism.

FIG. 15 shows a perspective view of a first embodiment of the holdingunit of the glass base material manufacturing apparatus 200.

FIG. 16 shows a part of a plan view of the holding unit 310 shown inFIG. 15.

FIG. 17 shows another embodiment of the holding unit 310.

FIG. 18 shows other further embodiments of the holding unit 310.

FIG. 19 shows other further embodiments of the holding unit 310.

FIG. 20 shows other further embodiments of the holding unit 310.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described based on the preferred embodiments,which do not intend to limit the scope of the present embodiment, butexemplify the invention. All of the features and combinations thereofdescribed in the embodiment are not necessarily essential to theinvention.

FIG. 4 shows an example of the glass base material manufacturingapparatus 200 of the present embodiment. The glass base materialmanufacturing apparatus 200 has chucks 12, motors 14, 20, and 118,burners 22A–22K, gas flow rate control units 52A–52K, raw material gassupply sources 88A–88G, a control unit 102, a first moving mechanism 48,a second moving mechanism 50, and a reaction vessel 210.

The chucks 12 hold the starting base material 2. The motor 14 rotatesthe starting base material 2 by rotating the chucks 12 around the axisof the starting base material 2.

The burners 22A–22K are arranged in a row at predetermined intervalsalong the longitudinal direction of the starting base material 2 on astand 15. The burners 22A–22K move reciprocatory over a section of thewhole length of the starting base material 2 while moving the turningposition of the reciprocatory movement along the longitudinal directionof the starting base material 2. That is, the burners 22A–22K of thepresent embodiment move reciprocatory according to the partial traversemethod. The burners 22A–22K form the deposit 10 by depositing glass sooton the starting base material 2.

The first moving mechanism 48 has a first moving axis 16 arrangedparallel with the longitudinal direction of the starting base material2. The first moving mechanism 48 moves the stand 15 reciprocatory with afirst cycle parallel with the longitudinal direction of the startingbase material by rotating the first moving axis 16 by the motor 118.Here the cycle means the time interval required for one lap of thereciprocate movement of the burners 22A–22K. The second moving mechanism50 is provided on the lower part of the first moving mechanism 48, andthe second moving mechanism 50 moves the first moving mechanism 48reciprocatory. The second moving mechanism 50 has a second moving axis18 arranged in parallel with the longitudinal direction of the firstmoving axis 16.

The second moving mechanism 50 moves the first moving mechanism 48reciprocatory with a second cycle, which is longer than the first cycle,by rotating the second moving axis 18 using the motor 20. Therefore, thefirst moving mechanism 48 moves the burners 22A–22E reciprocatory at afast speed, and the second moving mechanism 50 moves the first movingmechanism 48 reciprocatory at a speed slower than the first movingmechanism.

The gas flow control units 52A–52K are connected to correspondingburners 22A–22K, respectively. The gas flow control units 52A–52K supplyraw material gas to corresponding burners 22A–22K, respectively. As rawmaterial gas, the gas, which is raw material of glass soot, combustiongas, and assist combustion gas are supplied to a burner. Theraw-material-gas-supply-sources 88A–88G supply seven types of differentraw material gas, respectively, to each of the gas flow control units52A–52K. As shown in FIG. 4, since the raw-material-gas-supply-sources88A–88G is connected to all the gas flow control units 52A–52K,respectively, the raw-material-gas-supply-sources 88A–88G supply seventypes of different raw material gas to all the gas flow control units52A–52K, respectively.

Each of the gas flow control units 52A–52K has a plurality of flowrateregulators 74, 76, 78, 80, 82, 84, and 86, respectively. For example,the gas flow control unit 52A has the flow rate regulators 74A, 76A,78A, 80A, 82A, 84A, and 86A. The flow rate regulators 74A, 76A, 78A,80A, 82A, 84A, and 86A are connected to the correspondingraw-material-gas-supply-sources 88A–88G, respectively. Therefore, theflow rate regulators 74A, 76A, 78A, 80A, 82A, 84A, and 86A control theflow of different types of the raw material gas supplied from thecorresponding raw-material-gas-supply-sources 88A–88G, respectively.

A part of the raw material gas supplied from theraw-material-gas-supply-sources 88A–88G, the flow of which wascontrolled by each of the flow rate regulators 74A, 76A, 78A, 80A, 82A,84A, and 86A, respectively, joins and is supplied to the burner 22A. Theraw material gas, which does not join, such as fuel gas and assistcombustion gas, is supplied to each of plurality of the nozzles in theburner 22A. In the example shown in FIG. 4, the raw material gassupplied from the flow rate regulators 82A, 84A, and 86A is joined andsupplied to the nozzle of the burner 22A. Each raw material gas suppliedfrom the flow rate regulators 74A, 76A, 78A, and 80A is separatelysupplied to the corresponding nozzles of the burner 22A. The embodimentfor supplying the raw material gas to the burner 22 is not restricted tothe example shown in FIG. 4, and other embodiments may be used.

Since the gas flow control units 52B–52K have the same configurationwith that of the gas flow control unit 52A, the explanation of which isabbreviated. Moreover, since the configuration inside the gas flowcontrol units 52B–52K is same as that of the gas flow control unit 52A,the configuration inside the gas flow control units 52B–52K is not shownin FIG. 4.

Moreover, the quantity of the raw material gas supplied to each burner22A–22K may be controlled using other means, without using the flow rateregulators 74, 76, 78, 80, 82, 84, and 86 shown in FIG. 4. For example,the amount of raw material gas supplied to each burner 22A–22K may beadjusted by arranging the distribution unit for each of the burners22A–22K and further arranging the adjustable valve or orifice on thepiping, which extends from the distribution unit to each burner 22A–22K,and increasing or decreasing the pressure loss of a valve or an orifice.

The control unit 102 is connected to each of the flow rate regulators74, 76, 78, 80, 82, 84, and 86 of the gas flow control units 52A–52K.For example, the control unit 102 is connected to each of the flow rateregulators 74A, 76A, 78A, 80A, 82A, 84A, and 86A inside the gas flowcontrol unit 52A. The control unit 102 controls individually the flow inthe flow rate regulators 74, 76, 78, 80, 82, 84, and 86, respectively.The control unit 102 does not need to control all the flow rateregulators 74, 76, 78, 80, 82, 84, and 86, and may control some of theflow rate regulators.

The control unit 102 may control the flow rate regulators 74, 76, 78,80, 82, 84, and 86 so that the quantity of the raw material gas suppliedto burners 22A–22K changes with the progress of time. For example, theflow rate of the raw material gas to be supplied may be changedaccording to the growth of the deposition of glass soot in each stagesof early stage, middle stage, and later stage. The control unit 102 isconnected to the motors 14, 20, and 118, and the control unit 102controls the rotation speed of a chuck 12, the first moving axis 16, andthe second moving axis 18.

The reaction vessel 210 accommodates a chuck 12 and the burners 22A–22K.The reaction vessel 210 protects the composing elements of the glassbase material manufacturing apparatus 200 by isolating the composingelements of the glass base material manufacturing apparatus 200, such asthe first moving mechanism 48, the second moving mechanism 50, and thegas flow control units 52A–52K, from the heat generated during thereaction of the raw material gas. The reaction vessel 210 does not needto accommodate all the above-mentioned elements, and the reaction vessel210 may accommodate a part of above-mentioned elements.

Furthermore, the glass base material manufacturing apparatus 200 may beconnected to the preform analyzer 100, which measures the outsidediameter and the core diameter of the glass base material. The deposit10 manufactured by the glass base material manufacturing apparatus 200is sintered to be a glass base material by the sintering apparatus,which is provided separately with the glass base material manufacturingapparatus 200.

The outside diameter and the core diameter are measured by the preformanalyzer 100, which is provided separately with the glass base materialmanufacturing apparatus 200. The data related to the outside diameterand the core diameter of the glass base material can be input to thecontrol unit 102 from the preform analyzer 100 by connecting the preformanalyzer 100 to the control unit 102. The control unit 102 may controleach flow rate of the flow rate regulators 74, 76, 78, 80, 82, 84, and86 based on the data related to the outside diameter and the corediameter of the glass base material which is input from the preformanalyzer 100.

FIG. 5 shows the trajectory of the burner 22A by the reciprocatorymovement of the burner 22A. The glass base material manufacturingapparatus 200 shown in FIG. 4 has 11 burners 22A–22K. However, in orderto simplify the explanation, only one moving trajectory of the burner22A is shown. A vertical axis shows the progress of time and ahorizontal axis shows the moving distance of the burner 22A.

The first moving mechanism 48 moves the burner 22A reciprocatory withthe first cycle as shown by the solid line in FIG. 5. The moving widthof the first moving cycle is a part of the section to the whole lengthof the starting base material 2. The second moving mechanism 50 movesthe first moving mechanism 48 reciprocatory with the second cycle asshown by the hidden line in FIG. 5. The moving width of the secondmoving cycle is also a part of the section to the whole length of thestarting base material 2. At least one of the moving width of the firstmoving mechanism 48 and the moving width of the second moving mechanism50 is preferably to be an integral multiple of an interval among theinstalled burners. The moving width of the second moving cycle ispreferably to be an integral multiple of the interval of each of theburners 22A–22K. For example, it can be from once to twice of theinterval of each of the burners 22A–22K.

Although the moving width of the first moving cycle is smaller than themoving width of the second moving cycle in FIG. 5, the moving width ofthe first moving cycle may be equal to the moving width of the secondmoving cycle. The trajectory of the movement of the burner 22A becomes atrajectory, which is obtained by the superposition of the trajectory ofthe first cycle shown by a solid line on the trajectory of the secondcycle shown by a hidden line. Therefore, since the glass base materialmanufacturing apparatus 200 of the present embodiment has the firstmoving mechanism 48 and the second moving mechanism 50, it can move theturning position of the reciprocatory movement of the burners 22A–22K.

FIG. 6 shows a process for manufacturing the glass base material usingthe glass base material manufacturing apparatus 200 shown in FIG. 4.First, the deposit of the first batch is generated by supplying the rawmaterial gas to each burner 22A–22K with a basic flow rate anddepositioning glass soot on the starting base material (S10). The basicflow rate is a flow rate, in which the supply amount of the raw materialgas supplied to each burners 22A–22K is made to be equal ignoring thepressure loss, which is different for each of the burners 22A–22.Therefore, the control unit 102 provides the same output signal to eachgas flow control units 52A–52K even if the pressure loss is differentfor each of the burners 22A–22. Therefore, the raw material gas havingthe same flow rate is supplied to each of the burners 22A–22K,respectively, from the corresponding gas flow control units 52A–52K.

Next, the first batch of the glass base material is generated byheat-treating and vitrifying the first batch of the deposit generated bythe deposition of the first batch (S10) using the sintering apparatus,which is not shown in figures and is provided separately with the glassbase material manufacturing apparatus 200 (S12).

The relationship between the thickness of the deposit 10 and thethickness of the glass base material after the vitrification is changedwith the bulk density of a deposit. Therefore, it is difficult to judgewhether the amount of deposition of the deposit 10 is uniform along thelongitudinal direction of the starting base material 2 in the stagebefore vitrifying the deposit 10 into a transparent glass.

Furthermore, the refractive-index distribution inside the glass basematerial is obtained by transmitting such as laser light through theglass base material using the preform analyzer 100, provided separatelywith the glass base material manufacturing apparatus 200 and measuring agap of the position of the light which was transmitted through the glassbase material. The outside diameter of the glass base material can beobtained from the obtained refractive-index distribution. Therefore, thepreform analyzer 100 cannot be used for the white and porous deposit 10at the stage before vitrifying the deposit 10 because the light cannottransmit through the deposit 10. Therefore, in order to judge whetherthe amount of deposition of the deposit 10 is uniform along thelongitudinal direction of the starting base material 2 using the preformanalyzer 100, it is necessary to sinter and vitrify the deposit 10 intotransparent glass.

Next, the outside diameter and the core diameter of the first batch ofthe glass base material are measured (S14). For example, the outsidediameter of the first batch of the glass base material and the outsidediameter or the core diameter of the first batch of the starting basematerial 2 are measured using the preform analyzer 100. The distributionof the ratio between the outside diameter of the first batch of theglass base material and the outside diameter or the core diameter of thefirst batch of the starting base material, i.e., a deposition ratiodistribution, is measured by this measurement. The depositioncharacteristic of the glass soot of each burner 22A–22K can be known bycoordinating the measured deposition ratio distribution to thedeposition range of each burner 22A–22K.

A deposition ratio distribution is calculated based on the followingformulas.A rate of a core rod=(outside diameter of a starting basematerial)/(outside diameter of a glass base material)A deposition ratio=(1/rate of a core rod at a measurementposition)/(1/rate of a core rod at a standard position)

Here, “a core rod” in the formula means “the starting base material 2”.

Next, the correction value of the flow rate of the raw material gassupplied to the burners 22A–22K for the basic flow rate is calculatedfor each of the burners 22A–22K based on the deposition characteristicof each burner 22A–22K obtained from the calculated deposition ratiodistribution (S16). The correction value of the flow rate of the rawmaterial gas is calculated so that the deposition distribution of glasssoot becomes uniform along the longitudinal direction of the startingbase material 2. At a correction value calculation step (S16), acorrection value is calculated so that the adjustment range becomes 50%or less of the basic flow rate. When the adjustment range exceeds 50%and when the amount of supply of the raw material gas is differentbetween a certain burner and an adjoining burner, a defect may generatedduring sintering the glass base material.

Next, the second batch of the deposit is generated by supplying the rawmaterial gas to the burners 22A–22K, respectively, and depositing glasssoot on the starting base material 2 according to the value, which isobtained by correcting the correction value calculated in the correctionvalue calculation step (S16), to the basic flow rate (S18). Whiledepositing the second batch (S18), the basic flow rate may be changedaccording to the progress of time. However, while depositing the secondbatch (S18), the correction value of the flowrate of the raw materialgas supplied to each burner is not changed with the time. That is, oncethe correction value is set to each flow rate regulators 74, 76, 78, 80,82, 84, and 86, the correction value is not changed until the depositionof the second batch (S18) is completed.

Next, the second batch of the glass base material is generated byvitrifying the second deposit generated by the deposition of the secondbatch (S18) using a sintering apparatus (S20). Next, the diameter andthe core diameter of the second batch of the glass base material aremeasured, and a deposition ratio distribution is calculated (S22).

Next, a correction value is calculated for each of the burners 22A–22Kbased on the ratio of the deposition ratio of the first batch of theglass base material corresponding to each position of the burners22A–22K and the deposition ratio of the second batch of the glass basematerial corresponding to each position of the burners 22A–22K (S24).First, the rate of change of the deposition ratio of the first batch ofthe glass base material and the deposition ratio of the second batch ofthe glass base material in each position of the burners 22A–22K iscalculated. The rate of change of the ratio of this deposition ratioshows the rate of change of the ratio between the deposit amount ofglass soot in the first glass base material and the deposit amount ofglass soot in the second glass base material in each position of theburners 22A–22K. The formula for calculating the rate of change of theratio of the deposit amount of the glass soot is shown below.Rate-of-change of a deposition ratio=(deposition ratio of second glassbase material)/(deposition ratio of the first glass base material)

Next, the correction value of the flow rate of the raw material gassupplied to the burners 22A–22K is adjusted so that the depositiondistribution of glass soot may become uniform along the longitudinaldirection of the starting base material 2 based on the calculated rateof change of the deposition ratio.

Next, glass soot is deposited on the starting base material, and thethird batch of the deposit is generated by supplying the raw materialgas to the plurality of burners, respectively, based on the value, whichis obtained by correcting the correction value calculated in thecorrection value calculation step (S24) to the basic flow rate (S26).Here, while depositing the third batch (S26), the basic flow rate maybechanged according to the progress of time. However, while depositing thethird batch (S26), the correction value of the supply amount of the rawmaterial gas to each burner does not change with time. That is, once thecorrection value is set for each flow rate regulators 74, 76, 78, 80,82, 84, and 86, the correction value does not change until thecompletion of the third batch of the deposition (S26).

Next, the third batch of the glass base material is generated byvitrifying the third batch of the deposit manufactured by the thirdbatch of the deposition (S26) using the sintering apparatus (S28). Byrepeating the deposit sintering process and the correction valuecalculation process explained in the third batch of the deposition(S26), the third batch of the vitrification (S28), and a correctionvalue calculation step (S24) for a plurality of batches, the glass basematerial having a uniform deposition distribution of glass soot can bemanufactured. Moreover, the deposition process, the sintering process,and the correction value calculation process explained in the processesof the second batch of deposition (S18), the second batch ofvitrification (S20), and the correction value calculation (S16) may berepeated instead of repeating the deposition process, the sinteringprocess, and the correction value calculation process explained in thethird batch of the deposition (S26), the third batch of thevitrification (S28), and the correction value calculation step (S24).

As described above, the glass base material having a uniform depositiondistribution of glass soot can be manufactured by assuming and adjustingthe conditions, where the deposition distribution of glass soot becomesuniform along the longitudinal direction of the starting base material2, when number of batches of the glass base materials is actuallymanufactured.

Example 1

The deposit 10 was manufactured using the glass base materialmanufacturing apparatus 200 shown in FIG. 4. However, the number ofburners to be used was 10 instead of 11. The burner has been arrangedwith as interval of 150 mm. Therefore, the burners 22A–22J were usedamong the burners 22A–22K shown in FIG. 4. The deposit having an outsidediameter of average of 180 mm was manufactured by depositing glass sooton the starting base material 2 having outside diameter of 40 mm.

The amount of gas supplied to each burner 22A–22J was changed accordingto the increase in the outside diameter of the deposit 10. For example,in the early stages of deposition, the gas supply amount was controlledso that the supply amount of H2 to be 50 Nl/min, the supply amount of O2to be 30 Nl/min, and the supply amount of the raw material gas (SiCl4)to be 3.5 Nl/min. The gas supply amount was controlled so that thesupply amount of H2 to be 100 Nl/min, the supply amount of O2 to be 50Nl/min, and the supply amount of the raw material gas (SiCl4) to be 23Nl/min at the end of deposition.

The moving speed of the burners 22A–22J is set so that the moving speedof the first moving mechanism 48 to be 1,000 mm/min and the moving speedof the second moving mechanism 50 to be 20 mm/min. Moreover, both themoving width of the first moving mechanism 48 and the second movingmechanism 50 was set to be 150 mm. The distance between the burners22A–22J and the deposit 10 was set to be constant during the depositionof the glass soot on the starting base material 2.

Furthermore, the raw material gas of the same flow rate was supplied toall the burners 22A–22J by outputting the same signal to all the flowrate regulators 74–86 included in the gas flow control units 52A–52J.

Furthermore, the rotation speed of the starting base material 2 wascontrolled according to the increase in the outside diameter of thedeposit 10. For example, the rotation speed was controlled so that therotation speed to be 110 rpm at the time of starting the deposition andthe rotation speed to be 30 rpm at the time of end of deposition.

Glass base material was manufactured by manufacturing the deposit 10 andvitrifying the deposit 10 based on the above-mentioned settingconditions.

Example 2

As a result of measuring the deposition ratio distribution of Example 1using the preform analyzer 100, the deposition ratio at the positionscorresponding to the third burner 22C and the seventh burner 22G fromthe left, which are indicated by two arrows as shown in FIG. 7, waslower than the deposition ratio of other positions. Thus, the supplyconditions of the raw material gas over the burners 22C and 22G wereadjusted as follows so that the deposition ratio distribution to beuniform a long the longitudinal direction of the glass base material.

That is, each flow rate regulators 74–86 were set, respectively, so thatthe flow rate of the third burner 22C and the seventh burner 22G fromthe left among the 10 burners of 22A–22J becomes 1.20 times and 1.10times, respectively, of the flow rate of the other burners. This ratioof flow rate was kept constant during the deposition of the glass soot.The conditions other than the supply condition of the raw material gasto the burners 22C and 22G are set to be the same conditions withExample 1.

The deposit 10 having an average outside diameter of 180 mm wasmanufactured by depositing glass soot on the starting base material 2having outside diameter of 40 mm based on the above-mentioned settingconditions. Furthermore, the glass base material was manufactured byvitrifying the manufactured deposit 10 into transparent glass.

Example 3

As a result of measuring the deposition ratio distribution of Example 2,the deposition ratio around the region at the positions corresponding tothe third burner 22C and the seventh burner 22G from the left, which areindicated by two arrows as shown in FIG. 7 was lower than the depositionratio of the other positions. Thus, the supply conditions of the rawmaterial gas of the burners 22A–22J were adjusted as follows so that thedeposition ratio distribution along the longitudinal direction of theglass base material becomes uniform.

That is, each flow rate regulators corresponding to each burners 22A–22Jare adjusted so that the supply conditions of the burners 22A–22J areset such that the supply amount of the burner 22A is 1.04 times thebasic flow amount, and the supply amount of the burner 22B is 1.04 timesthe basic flow amount, and the supply amount of the burner 22C is 1.08times the basic supply amount, and the supply amount of burner 22D is0.97 times the basic supply amount, and the supply amount of the burner22E is 0.90 times the basic supply amount, and the supply amount of theburner 22F is 0.97 times the basic supply amount, and the supply amountof burner 22G is 1.18 times the basic supply amount, and the supplyamount of the burner 22H is 1.00 times the basic supply amount, and thesupply amount of the burner 22I is 0.93 times the basic supply amount,and the supply amount of the burner 22J is 0.90 times the basic supplyamount where the basic supply amount is assumed to be 1. This flow rateratio was kept constant during the deposition of the glass soot. All theconditions other than the supply condition of the raw material gas wereset as the same conditions with Example 2.

The deposit 10 having an average outside diameter of 180 mm wasmanufactured by depositing glass soot on the starting base material 2having an outside diameter of 40 mm based on the above-mentioned settingconditions. Furthermore, a glass base material was manufactured byvitrifying the manufactured deposit 10 into transparent glass.

FIG. 7 shows the change of each deposition ratio of Example 1 andExample 2. The line with square points in FIG. 7 shows the depositionratio distribution, which is obtained by measuring the glass basematerial manufactured in Example 2 using the preform analyzer 100. Onthe other hand, the line with triangular points indicates the depositionratio distribution, which is obtained by measuring the glass basematerial manufactured in Example 1 using the preform analyzer 100. Thearrow in the figure corresponds to the position of the third and theseventh burners 22C and 22G from the left, respectively.

Since the deposition ratio in the range corresponding to the positionsof the third burner 22C and the seventh burner 22G from the left shownby the arrow is low in Example 1 as shown in FIG. 7, the amount ofdeposition of glass soot is not uniform along the longitudinal directionof the glass base material.

Therefore, in Example 2, the supply amount of the raw material gas tothe third burner 22C and the seventh burner 22G from the left wasincreased by adjusting the flow rate regulators 74C–86C and 74G–86Gincluded in the gas flow control units 52C and 52G, respectively.Therefore, it can be understood that the deposition ratio of Example 2increased compared with the deposition ratio of Example 1 when thedeposition ratio is compared at the positions of the burners 22C and 22Gshown by the arrow. That is, it can be understood that the amount ofdeposition of the glass soot of Example 2 increased compared with theamount of deposition of the glass soot of Example 1 in the rangecorresponding to the positions of the burners 22C and 22G. Since theamount of deposition of the glass soot of the burners 22C and 22Gincreased, the deposition ratio distribution of Example 2 became uniformin the longitudinal direction of the glass base material compared withthe deposition ratio distribution of Example 1.

FIG. 8 shows the rate of change of the deposition ratio of Example 1 andthe deposition ratio of Example 2. That is, FIG. 8 shows the degree ofpartial increase of the deposition ratio of Example 2 over thedeposition ratio of Example 1. In order to obtain the rate of change ofthe deposition ratio, the rate of change of the deposition ratio ofExample 2 over the deposition ratio of Example 1 was obtained for eachposition of burners 22A–22J. As shown in FIG. 8, the rate of change atthe part shown by the arrow that corresponds to the third burner 22C andthe seventh burner 22G increased.

FIG. 9 shows the change of deposition ratio in Example 3 and Example 1.The line with square points in FIG. 9 shows the deposition ratiodistribution, which is obtained by measuring the glass base materialmanufactured in Example 3 using the preform analyzer 100. On the otherhand, the line with triangular points shows the deposition ratiodistribution, which is obtained by measuring the glass base materialmanufactured in Example 1 using the preform analyzer 100. The supplyamount of the raw material gas to each burner 22A–22G was adjusted inExample 3 based on the result of Example 2. Therefore, as shown in FIG.9, the deposition ratio distribution of Example 3 became substantiallyuniform along the longitudinal direction of the glass base material.

FIG. 10 shows the rate of change between the deposition ratio of Example3 and the deposition ratio of Example 1. That is, FIG. 10 shows thedegree of partial increase of the deposition ratio of Example 3 over thedeposition ratio of Example 1. In order to obtain the above-mentionedrate of change of the deposition ratio, the rate of change of thedeposition ratio of Example 3 over the deposition ratio of Example 1 isobtained for each position of the burners 22A–22J. It is understood thatthe rate of change of each burner 22A–22J of Example 3 increased aroundthe burner 22C and burner 22G as shown in FIG. 10.

Example 1 corresponds to manufacturing the first batch of the glass basematerial by the first batch of the deposition (S10) and the first batchof the vitrification (S12) if the above-explained Example 1, Example 2,and Example 3 refer to the flow chart of FIG. 6. Furthermore, Example 2corresponds to manufacturing the second batch of the glass base materialby the measurement of the outside diameter and the core diameter of thefirst batch of the glass base material (S14), the calculation of thecorrection value (S16), the deposition of the second batch (S18), andthe vitrification of the second batch (S20). Furthermore, Example 3corresponds to manufacturing the third batch of the glass base materialby the measurement of the outside diameter and the core diameter of thethird batch of the glass base material (S22), calculation of thecorrection value (S24), third batch of the deposition (S26), andvitrification of the third batch (S28).

Therefore, it can be understood that the deposition ratio distributionof glass soot becomes further uniform as shown in FIGS. 7 and 9 everytime when the correction value is adjusted in Example 1, Example 2 andExample 3. Therefore, the lass base material having uniform depositionratio distribution can be manufactured according to the embodiment shownfrom FIG. 4 to FIG. 6.

FIG. 11 shows an embodiment of the deformation reduction mechanism ofthe glass base material manufacturing apparatus 200. FIG. 11A shows aperspective view of the glass base material manufacturing apparatus 200.FIG. 11B shows a plane view of the glass base material manufacturingapparatus 200. FIG. 11C shows the sectional view that enlarges theflexural structure part 204 seen from the direction of the arrow A ofFIG. 11A. The glass base material manufacturing apparatus 200 in FIG. 11has the similar configuration with that of the glass base materialmanufacturing apparatus 200 shown in FIG. 4 except the configuration ofthe reaction vessel 210. Thus, the configurations other than thereaction vessel 210, the deposit 10, a burner 22, and a deformationreduction mechanism of the glass base material manufacturing apparatus200 are abbreviated in order to simplify the explanation in FIG. 11.Moreover, in order to simplify the explanation, the configuration of theburner 22 is simplified.

If the deposit 10 is manufactured using the glass base materialmanufacturing apparatus 200, the temperature inside of the glass basematerial manufacturing apparatus 200 increases due to the heat generatedwhen the burner 22 generates glass soot. For example, the temperatureinside the apparatus reaches hundred degrees during the deposition ofthe glass soot, and the temperature inside the apparatus returns to roomtemperature after the deposition of the glass soot. Deformation orcracks caused by the heat stress may occur on parts that form theapparatus, especially the reaction vessel 210, by the repetition of therapid rise and fall of the temperature in the apparatus, i.e., heatcycle. Therefore, not only the heat cycle has bad influence on thecharacteristic of the manufactured deposit 10, but also it may becomeimpossible to work the glass base material manufacturing apparatus 200because of the damage to the reaction vessel 210.

Thus, by providing a deformation reduction mechanism on the reactionvessel 210, the deformation reduction mechanism can prevent thedeformation or damage to the apparatus since the deformation reductionmechanism absorbs, distributes, or suppresses the heat stress in thereaction vessel 210.

The deformation reduction mechanism shown in FIG. 11 includes a flexuralstructure part 204, which is formed in the reaction vessel 210. As shownin FIG. 1C, the section of the flexural structure part 204 has aflexural structure such that the section expands outside from thesurface of a wall of a reaction vessel. Furthermore, the flexuralstructure part 204 is formed around the reaction vessel 210 so that theflexural structure part 204 surrounds the reaction vessel 210. That is,the section of the reaction vessel 210 is halved at the flexuralstructure part 204 as a border. Furthermore, the section of the reactionvessel 204 may be divided into a plurality parts by forming the flexuralstructure part 204 in the plurality of places of the reaction vessel204. The flexural structure part 204 can prevent the deformation ordamage on an apparatus by absorbing the expansion caused by the heatinside the reaction vessel 210.

The flexural structure part 204 is formed by the same material with thematerial of the reaction vessel 210. For example, it is preferable touse nickel material (Ni) as a material used for the flexural structurepart 204. Moreover, stainless steel material may be used for theflexural structure part 204. Furthermore, the flexural structure part204 may be formed by the material, which is different from the materialof the reaction vessel 210.

FIG. 12 shows other embodiments of a deformation reduction mechanism.FIG. 12A shows a perspective view of the glass base materialmanufacturing apparatus 200. FIG. 12B shows the plan view of the glassbase material manufacturing apparatus 200. FIG. 12C shows the expandedsectional view of the deformation restriction unit 212 seen from thedirection of the arrow A in FIG. 12A.

The glass base material manufacturing apparatus 200 of FIG. 12 has aconfiguration similar to the glass base material manufacturing apparatus200 shown in FIG. 4 except the reaction vessel 210. Thus, theconfiguration other than the reaction vessel 210, the deposit 10, theburner 22, and the deformation reduction mechanism of the glass basematerial manufacturing apparatus 200 is abbreviated in FIG. 12 in orderto simplify the explanation. Moreover, in order to simplify theexplanation, the configuration of the burner 22 shown in the figure issimplified.

The deformation reduction mechanism shown in FIG. 12 has a deformationrestriction unit 212, which restricts the deformation of the reactionvessel 210. As shown in FIG. 12C, the square shaped hollow steel pipe isused for the deformation restriction unit 212. Moreover, as long as itcan restrict the deformation of the reaction vessel 210, the members,such as channel or H-beam other than a square shape steel pipe may beused as a deformation restriction unit 212.

Two deformation restriction units 212 are formed so that each of thedeformation restriction units 212 surrounds the circumference of thereaction vessel 210 and restricts the deformation of the reaction vessel210. The deformation caused by the heat stress of the reaction vessel210 is restricted in the upper and lower direction, right and leftdirection, and back and forth direction by providing two deformationrestriction units 212 that surround the circumference of the reactionvessel 210 in the direction orthogonal with each other. The deformationrestriction unit 212 suppresses the reaction vessel 210 so that the heatstress, which is generated by the heat cycle inside the reaction vessel210, does not damage and deform the reaction vessel 210.

Carbon steel or stainless steel is used as a material of the deformationrestriction unit 212. Materials other than carbon steel or stainlesssteel having a low linear expansivity such as from 1.2×10⁻⁵/° C. to1.8×10⁻⁵/° C. may be used for the deformation restriction unit 212.

FIG. 13 shows other embodiments of a deformation reduction mechanism.FIG. 13A shows a perspective view of the glass base materialmanufacturing apparatus 200. FIG. 13B shows a plan view of the glassbase material manufacturing apparatus 200. FIG. 13C shows an expandedsectional view of the curved wall 214 seen from the direction of thearrow A in FIG. 13A.

The glass base material manufacturing apparatus 200 of FIG. 13 has thesimilar configuration with the glass base material manufacturingapparatus 200 shown in FIG. 4 except the reaction vessel 210. Thus, theconfigurations other than the reaction vessel 210, the deposit 10, theburner 22, and the deformation reduction mechanism of the glass basematerial manufacturing apparatus 200 are abbreviated in FIG. 13 in orderto simplify the explanation. Moreover, in order to simplify explanation,the configuration of the burner 22 is simplified and shown in the FIG.13.

The reaction vessel 210 has the curved wall 214, which has acontinuously curved form as the deformation reduction mechanism. Asshown in FIG. 13C, the curved wall 214 is formed by a large number ofcontinuous flexural surface. Because the reaction vessel 210 has thecurved wall 214, the heat stress generated by the heat cycle in thereaction vessel 210 is distributed in each curved surface part of thecurved surface structure and does not concentrate on one point.Therefore, the curved wall 214 can suppress the damage and deformationof a reaction vessel caused by the heat stress.

FIG. 14 shows other embodiments of a deformation reduction mechanism.FIG. 14A shows a perspective view of the glass base materialmanufacturing apparatus 200. FIG. 14B shows a plan view of the glassbase material manufacturing apparatus 200. FIG. 14C shows an expandedsectional view of the slide part 216 seen from the direction of thearrow A of FIG. 14A. The glass base material manufacturing apparatus 200of FIG. 14 has the similar configuration with the glass base materialmanufacturing apparatus 200 shown in FIG. 4 except the reaction vessel210. Thus, the configurations other than the reaction vessel 210, thedeposit 10, the burner 22, and the deformation reduction mechanism ofthe glass base material manufacturing apparatus 200 is abbreviated inFIG. 14 in order to simplify the explanation. Moreover, in order tosimplify the explanation, the configuration of the burner 22 issimplified and shown in the FIG. 14.

The reaction vessel 210 has a slide part 216, in which a part of thewalls of the reaction vessel 210 overlaps and slides, as the deformationreduction mechanism. The reaction vessel 210 has the slide part 216around the reaction vessel 210 so that the slide part 216 surrounds thereaction vessel 210. Since a part of the walls of the reaction vessel210 overlaps and slides by the slide part 216, the heat stress generatedby the heat cycle in a reaction vessel is distributed by the sliding andis not accumulated. Therefore, the damage and the deformation of thereaction vessel 210 are suppressed.

Example 1

The deposit 10 was manufactured using the glass base materialmanufacturing apparatus 200, which has the flexural structure part 204as shown in FIG. 11. The starting base material 2 having a length of 500mm and an outside diameter of 25 mm manufactured using the VAD methodwas prepared. The starting base material 2 was held by the chuck 12. Theraw material gas, fuel gas, and assist combustion gas of 10 L/minute ofSiCl₄, 100 L/minute of O₂, and 200 L/minute of H₂ were supplied to theburners 22A–22K. The glass soot was deposited on the starting basematerial 2 while the starting base material 2 was rotated with the speedof 10 times/minute, and the burners 22A–22K were moved reciprocatorywith a speed of 50 mm/minute along the longitudinal direction of thestarting base material 2. The deposit 10 having an outside diameter of150 mm was obtained by the above-mentioned process of depositing theglass soot.

While depositing the glass soot on the starting base material 2, thetemperature inside the reaction vessel 210 was changed within a rangebetween 80° C. and 310° C., and the temperature inside the reactionvessel 210 decreased to 30° C. at the end of the deposition. Thisdeposition process was repeated for 100 times. The deformation of thereaction vessel 210 caused by the heat stress inside the reaction vessel210 was suppressed to 1 mm. The crack caused by the heat stress was notgenerated in the reaction vessel 210. Moreover, no impure particles weremixed in the manufactured deposit 10, which was accompanied by thedamage and the crack of the reaction vessel 210. Therefore, there wasalso no pore shaped defect caused by the mixing of impure particles intothe manufactured deposit 10.

Example 2

The deposit 10 was manufactured using the glass base materialmanufacturing apparatus 200, which has the deformation restriction unit212 as shown in FIG. 12. The deposit 10 having an outside diameter of150 mm was manufactured according to the same conditions as Example 4except the glass base material manufacturing apparatus 200 having thedeformation restriction unit 212 as a deformation reduction mechanism.

While depositing the glass soot on the starting base material 2, thetemperature in the reaction vessel 210 changed within a range between80° C. to 310° C., and the temperature in the reaction vessel 210decrease to 30° C. at the end of the deposition. This deposition processwas repeated for 120 times. The deformation of the reaction vessel 210caused by the heat stress inside the reaction vessel 210 was suppressedto 1 mm. The crack caused by the heat stress was not generated in thereaction vessel 210. Moreover, no impure particles were mixed in themanufactured deposit 10, which was accompanied by the damage and thecrack of the reaction vessel 210. Therefore, there was also no poreshaped defect caused by the mixing of impure particles into themanufactured deposit 10.

Example 3

The deposit 10 was manufactured using the glass base materialmanufacturing apparatus 200, which has the curved wall 214 as shown inFIG. 13. The deposit 10 having an outside diameter of 150 mm wasmanufactured according to the same conditions as Example 4 except theglass base material manufacturing apparatus 200 having the curved wall214 as a deformation reduction mechanism.

While depositing the glass soot on the starting base material 2, thetemperature in the reaction vessel 210 changed within a range between80° C. to 310° C., and the temperature in the reaction vessel 210decreased to 30° C. at the end of the deposition. This depositionprocess was repeated for 120 times. The deformation of the reactionvessel 210 caused by the heat stress inside the reaction vessel 210which was suppressed to 1 mm. The crack caused by the heat stress wasnot generated in the reaction vessel 210. Moreover, no impure particleswere mixed in the manufactured deposit 10, which was accompanied by thedamage and the crack of the reaction vessel 210. Therefore, there wasalso no pore shaped defect caused by the mixing of impure particles intothe manufactured deposit 10.

Example 4

The deposit 10 was manufactured using the glass base materialmanufacturing apparatus 200, which has the slide part 216 as shown inFIG. 14. The deposit 10 having an outside diameter of 150 mm wasmanufactured according to the same conditions as Example 4 except theglass base material manufacturing apparatus 200 having the slide part216 as a deformation reduction mechanism.

While depositing the glass soot on the starting base material 2, thetemperature in the reaction vessel 210 changed within a range between80° C. to 310° C., and the temperature in the reaction vessel 210decreased to 30° C. at the end of the deposition. This depositionprocess was repeated for 130 times. The deformation of the reactionvessel 210 caused by the heat stress inside the reaction vessel 210which was suppressed to 1 mm. The crack caused by the heat stress wasnot generated in the reaction vessel 210. Moreover, no impure particleswere mixed in the manufactured deposit 10, which was accompanied by thedamage and the crack of the reaction vessel 210. Therefore, there wasalso no pore shaped defect caused by the mixing of impure particles intothe manufactured deposit 10.

Example 5

The deposit 10 was manufactured using the glass base materialmanufacturing apparatus 200, which has the curved wall 214 as shown inFIG. 13. The deposit 10 having an outside diameter of 150 mm wasmanufactured according to the same conditions as Example 4 except theglass base material manufacturing apparatus 200 having the curved wall214 as a deformation reduction mechanism.

While depositing the glass soot on the starting base material 2, thetemperature in the reaction vessel 210 changed within a range between80° C. to 310° C., and the temperature in the reaction vessel 210decreased to 30° C. at the end of the deposition. This depositionprocess was repeated for 170 times. The deformation of the reactionvessel 210 caused by the heat stress inside the reaction vessel 210which was suppressed to 1 mm. The crack caused by the heat stress wasnot generated in the reaction vessel 210. Moreover, no impure particleswere mixed in the manufactured deposit 10, which was accompanied by thedamage and the crack of the reaction vessel 210. Therefore, there wasalso no pore shaped defect caused by the mixing of impure particles intothe manufactured deposit 10.

Comparative Example 1

The deposit 10 was manufactured using the conventional glass basematerial manufacturing apparatus which does not have the deformationreduction mechanism shown from FIG. 11 to FIG. 14. The deposit 10 havingan outside diameter of 150 mm was manufactured according to the sameconditions as Example 4 except that the glass base materialmanufacturing apparatus 200 did not have the curved wall 214 as adeformation reduction mechanism.

While depositing the glass soot on the starting base material 2, thetemperature in the reaction vessel 210 changed within a range between80° C. to 310° C., and the temperature in the reaction vessel 210decreased to 30° C. at the end of the deposition. This depositionprocess was repeated for 40 times. The deformation of the reactionvessel 210 caused by the heat stress inside the reaction vessel 210reached to 25 mm. The crack caused by the heat stress was generated infive places in the reaction vessel 210. Moreover, many pore shapeddefects, which were caused by mixing of impure particles into themanufactured deposit 10 accompanied by the damage and the crack of thereaction vessel 210, were generated in the manufactured deposit 10.Therefore, the manufactured deposit 10 could not be used as a product.

As explained above, the deformation, crack, and damage of the reactionvessel 210 caused by the heat stress can be decreased by providing thedeformation reduction mechanism in the reaction vessel 210. Therefore,the deformation reduction mechanism can prevent the impure particlesfrom being mixed in a deposit that produces a pore shaped defect, whichis caused by the deformation, crack, and damage of the reaction vessel210. Moreover, since the deformation reduction mechanism can extend theinterval of repair or renewal of the glass base material manufacturingapparatus 200, a high quality glass base material can be manufactured atlow cost.

FIG. 15 shows a perspective view of a first embodiment of the holdingunit of the glass base material manufacturing apparatus 200. FIG. 16shows a part of a plan view of the holding unit 310 shown in FIG. 15.The glass base material manufacturing apparatus 200 has a holding unit310, by which the deposit 10 is held and transported outside thereaction vessel 210. The deposit 10 has conical parts 306 both ends, andthe holding unit 310 has a means for holding a conical part 306.

For example, the holding unit 310 has three clamps 314 a–314 c, whichcan hold the conical part 306 by sandwiching the conical part 306 fromboth the upper and lower sides in the embodiment shown in FIG. 15. Theclamps 314 a–314 c can hold the conical part 306 from the upper andlower sides by rotating the clamps 314 a–314 c around the axis 316,which couples the clamps 314 a–314 c with each other. For example, theclamp 312 c presses the conical part 306 downwards, and the clamps 312 aand 312 b press the conical part 306 upwards.

Furthermore, the clamps 314 a–314 c are installed at the tip of the arm318, which has an axis 316. By moving the arm 318 horizontally, theclamps 314 a–314 c, which hold the deposit 10, can be movedhorizontally. Therefore, the deposit 10 can be transported outside thereaction vessel 210.

Furthermore, the clamps 314 a–314 c have concave parts 312 a–312 c,which have the angle substantially similar to the angle of a part of theinclination 320 of the conical part 306 shown in FIG. 16. The concavepart 312 a–312 c may have curved grooves as shown in FIG. 15. Moreover,the concave part 312 a–312 c may have substantially V-shaped grooves.Since the clamps 314 a–314 c have concave parts 312 a–312 c, the clamps314 a–314 c can hold the conical part 306 securely.

Because the holding unit 310 has a means for holding the conical part306, it can prevent damage and breakage of the deposit 10 when thedeposit 10 is held and transported using the holding unit 310.

For example, the conventional holding unit holds both ends of thestarting base material 2 when transporting the deposit 10. When thestarting base material 2 having a small outside diameter was held andraised, a crack occurred in the starting base material 2, and thedeposit 10 fell and broke due to the weight of a deposit.

On the other hand, if the cylindrical part 304 of the deposit 10 havinga large outside diameter and strength is held by the holding unit, thepores inside the deposit 10 may collapse, or the surface of the deposit10 may be damaged. The damage on the surface and the collapsed poresremain inside the glass base material, which is formed by vitrifying thedeposit, as uneven parts or bubbles. Since these uneven parts or thebubbles remaining in the glass base material need to be removed, theyield rate of the manufacturing of the glass base material manufacturedecreased due to the process of removing the uneven parts or bubbles.

Thus, the holding unit 310 of the present embodiment has a means forholding the conical part 306 of the deposit 10. The holding unit 310 cantransport the deposit 10 without damaging the cylindrical part 304 ofthe deposit 10 by holding the conical part 306 of the deposit 10.Furthermore, since the outside diameter of the conical part 306 islarger than that of the starting base material 2, and the strength theconical part 306 is larger than that of the starting base material 2,the holding unit 310 can prevent the fall and breakage of the deposit10, which is caused by a crack generated in the starting base material2, by holding the conical part 306.

FIG. 17 shows other embodiments of the holding unit 310. In addition tothe configuration of the holding unit 310 of FIG. 15, the holding unit310 has a mechanism for adjusting the position of the clamps 314 a–314 cin the axial direction of the deposit 10.

The mechanism for adjusting the position of the clamps 314 a–314 c hasan arm 318, which supports the clamps 314 a–314 c, and screw shaft 330,which moves the arm 318 in the axial direction of the deposit 10. Thescrew shaft 330 penetrates through the arm 318 and engages with the arm318. The screw shaft 330 is connected to the electric motor 336. The arm318 can be moved in the axial direction of the deposit 10 by rotatingthe screw shaft 330 using the electric motor 336. Furthermore, theposition adjustment mechanism has a guide axis 332, which penetratesthrough the arm 318 in parallel with the screw shaft 330.

By the above-mentioned configuration of FIG. 17, the holding unit 310can hold the conical part 306 at a suitable position by rotating thescrew shaft 330 using the electric motor 336 according to the length ofthe deposit 10 and moving the arm 318 in the axial direction of thedeposit 10.

FIG. 18 shows further other embodiments of the holding unit 310. Inaddition to the configuration of the holding unit 310 shown in FIG. 15,the holding unit 310 has a holding pressure adjustment unit for holdingthe conical part 306 with a substantially uniform pressure. For example,the holding pressure adjustment units are the elastic bodies 324 a–324 cformed on the face that contact with the conical part 306 of the clamps314 a–314 c in FIG. 18. By forming the elastic bodies 324 a–324 c on theface that contact with the conical part 306 of the clamps 314 a–314 c,the holding unit 310 can hold the conical part 306 securely even if theconical part 306 has uneven parts.

FIG. 19 shows further other embodiments of the holding unit 310. Theholding unit 310 has clamps 314 a and 314 c, which can hold the conicalpart 306 by sandwiching the conical part 306. The clamps 314 a and 314 chave concave part 312 a (not shown in the figure) and 312 c.Furthermore, the holding unit 310 has holding angle adjustment units 322a and 322 c for adjusting the angle of the concave part 312 a and 312 cof the clamps 314 a and 314 c to be substantially same with the angle ofa part of the inclination 320 of the conical part 306.

The holding angle adjustment units 322 a and 322 c rotate the clamps 314a and 314 c around the longitudinal direction of the clamps 314 a and314 c as an axis. The holding angle adjustment units 322 a and 322 cadjust the angle of the concave parts 312 a and 312 c of the clamps 314a and 314 c to be substantially same with the angle of the inclination320 of a part of the conical part 306 by rotating the clamps 314 a and314 c. Therefore, the holding unit 310 can hold the conical part 306securely by having the holding angle adjustment units 322 a and 322 c.Each holding angle adjustment units 322 a and 322 c may rotate theclamps 314 a and 314 c using an electric motor, respectively.

When holding the deposit 10, which has a large outside diameter shown bythe phantom line, the holding angle adjustment units 322 a and 322 crotate the clamps 314 a and 314 c in the direction shown by arrow. Atthis time, the holding angle adjustment units 322 a and 322 c rotate theclamps 314 a and 314 c so that the angle of the concave parts 312 a and312 c to be substantially same with the angle of the inclination 320 ofthe conical part 306. Therefore, the holding unit 310 can hold theconical part 306 securely by rotating the clamps 314 a and 314 c usingthe holding angle adjustment units 322 a and 322 c even if the deposits10 have different outside diameters.

FIG. 20 shows further other embodiments of the holding unit 310. Theholding pressure adjustment unit of FIG. 20 has a plurality of columnarobjects 326 a and 326 c each of which moves telescopically according tothe curved surface of the conical part 306. A plurality of columnarobjects 326 a and 326 c are installed in the corresponding clamps 314 aand 314 c, respectively. The tips 328 a and 328 c, the end of which areround, are formed at the tip of the columnar objects 326 a and 326 c inorder not to damage the surface of the deposit 10. Since the tips 328 aand 328 c of the plurality columnar objects 326 a and 326 c movetelescopically upwards and downwards according to the curved surface ofthe conical part 306, the holding unit 310 can hold the conical part 306with uniform pressure.

EXAMPLE

The deposit 10 manufactured using the glass base material manufacturingapparatus 200 was transported outside the glass base materialmanufacturing apparatus 200 using the holding unit 310 shown in FIG. 15.

Both ends of the starting base material 2 were held by the chuck 12 inthe reaction vessel 210. The deposit 10, which has the cylindrical part304 on the center and the conical parts 306 on both ends, wasmanufactured by depositing glass soot around the outside surface of thestarting base material 2 while rotating the starting base material 2.After the completion of the manufacture of the deposit 10, a practicablewindow 308 of the reaction vessel 210 was opened.

Next, two holding units 310 were inserted into the reaction vessel 210from the practicable window 308 by extending the arm 318 inside thereaction vessel 210. Each holding unit 310 held the correspondingconical part 306 formed on both ends of the deposit 10, respectively.Each holding units 310 sandwiched the conical part 306 by inserting theconcave part 312 a–312 c of the clamps 314 a–314 c into the conical part306. For this reason, the deposit 10 was supported by the holding unit310. Next, the chuck 12 was loosened, and the starting base material 2was removed from the chuck 12. The arm 318 was contracted, and thedeposit 10 was removed from the reaction vessel 210.

The track, to which the arm 318 was installed, was moved to thesintering apparatus for vitrifying the deposit 10 into transparentglass. By rotating or extending and contracting the arm 318, the deposit10 was installed at the predetermined position of the sinteringapparatus. Moreover, after the deposit 10 is removed from the reactionvessel 210, the deposit 10 maybe mounted on the track having the concavepart 312 a–312 c similar to the holding unit 310 for transportation.

100 deposits 10 having a full length of 1500 mm and a weight of 100 kgwere transported according to the above procedure using the holding unit310. No damage was found in the cylindrical part 304 of all the deposits10. Furthermore, no surface cracks or internal bubbles were found in thecylindrical part 304 of the deposits 10 when these 100 deposits 10 weresintered and vitrified into transparent glass.

Comparative Example

50 deposits 10 having a full length of 1500 mm and a weight of 100 kgwere transported. The cylindrical part 304 of the deposit 10 was heldand transported using the conventional holding unit. When thetransported deposits 10 were sintered, cracks were found on the surfaceof the cylindrical part 304 of 45 glass base materials among 50 of thesintered glass base materials. Moreover, remaining bubbles were foundinside the cylindrical part 304 of all 50 of the glass base materials.

Therefore, the deposit 10 can be transported without damaging thecylindrical 304 of the deposit 10 by using the holding unit 310 shownfrom FIG. 15 to FIG. 20.

The example for transporting the deposit 10 horizontally using theholding unit 310 was explained above. However, the transport directionof the deposit 10 is not limited to the horizontal direction, but thedeposit 10 may be transported by rotating the longitudinal direction ofthe deposit 10 from the horizontal direction to the vertical direction,and the deposit 10 may be transported where the longitudinal directionof the deposit 10 is continuously arranged in the vertical direction.

Although the present embodiment has been described by way of exemplaryembodiments, it should be understood that many changes and substitutionsmay be made by those skilled in the art without departing from thespirit and the scope of the present embodiment which is defined only bythe appended claims.

1. A glass base material manufacturing apparatus for manufacturing aglass base material, which is used as a base material of an opticalfiber, comprising: a plurality of burners, arranged in a row atpredetermined intervals along a longitudinal direction of a startingbase material of said glass base material, for forming a deposit, whichis a base material of said glass base material by depositing glass sooton said starting base material while moving reciprocatorily over asection of an entire length of said starting base material along thelongitudinal direction of said starting base material; a plurality offlow rate regulators, at least one of which is connected to saidplurality of burners, respectively, for regulating a flow rate of rawmaterial gas of said glass soot, which is supplied to said plurality ofburners; and a control module connected to each of said plurality offlow rate regulators for controlling individually said plurality of flowrate regulators, said control module comprising: a first control unitwhich controls a plurality of said flow rate regulators so that said rawmaterial gas of a base flow rate is supplied to said plurality of saidburners; and a second control unit which controls each of said pluralityof flow rate regulators according to a correction value of flow rate ofsaid raw material gas supplied to said burners, said correction valuebeing calculated for each of said plurality of burners over said baseflow rate.
 2. The glass base material manufacturing apparatus as claimedin claim 1, wherein said second control unit calculates said correctionvalue for each of said plurality of flow rate regulators based on adeposition ratio of said glass base material, which is formed byvitrifying said deposit actually deposited by said plurality of burners.3. The glass base material manufacturing apparatus as claimed in claim2, wherein said second control unit adjusts said correction value foreach of said plurality of flow rate regulators according to a ratiobetween a deposition ratio of first glass base material, which is formedby vitrifying said deposit formed by controlling said flow rateregulators using said first control unit corresponding to each positionsof said plurality of burners, and a deposition ratio of second glassbase material, which is formed by vitrifying said deposit formed bycontrolling said flow rate regulators using said first control unit andsaid second control unit.
 4. The glass base material manufacturingapparatus as claimed in claim 2, wherein said control module isconnected to a preform analyzer, which measures an outside diameter anda core diameter of said glass base material.
 5. The glass base materialmanufacturing apparatus as claimed in claim 1, wherein said secondcontrol unit calculates said correction value to be 50% or less of saidbase flow rate.
 6. The glass base material manufacturing apparatus asclaimed in claim 1, wherein said first control unit controls said flowrate regulator so that an amount of said raw material gas supplied tosaid burners is changed with progress of time.
 7. The glass basematerial manufacturing apparatus as claimed in claim 1, wherein saidplurality of flow rate regulators is connected to one of said burners.8. The glass base material manufacturing apparatus as claimed in claim7, wherein said plurality of flow rate regulators controls flow rate ofdifferent types of said raw material gas, respectively.
 9. The glassbase material manufacturing apparatus as claimed in claim 1, furthercomprising: a first moving mechanism that moves said plurality ofburners reciprocatorily in a first cycle along the longitudinaldirection of said starting base material; and a second moving mechanismthat moves said first moving mechanism reciprocatorily in a secondcycle, the cycle of said second cycle being longer than said firstcycle.
 10. A glass base material manufacturing apparatus formanufacturing a glass base material, which is used as a base material ofan optical fiber, comprising: a plurality of burners, arranged in a rowat predetermined intervals along a longitudinal direction of a startingbase material of said glass base material, for forming a deposit, whichis a base material of said glass base material by depositing glass sooton said starting base material while moving reciprocatorily over asection of an entire length of said starting base material along thelongitudinal direction of said starting base material; a plurality offlow rate regulators, at least one of which is connected to saidplurality of burners, respectively, for regulating a flow rate of rawmaterial gas of said glass soot, which is supplied to said plurality ofburners; a control module connected to each of said plurality of flowrate regulators for controlling individually said plurality of flow rateregulators; a reaction vessel which accommodates said plurality ofburners; and a deformation reduction mechanism, which reduces adeformation of, said reaction vessel caused by heat generated whenmanufacturing said glass base material.
 11. The glass base materialmanufacturing apparatus as claimed in claim 10, wherein said deformationreduction mechanism includes a flexural structure part formed in saidreaction vessel.
 12. The glass base material manufacturing apparatus asclaimed in claim 11, wherein said flexural structure part is formedaround said reaction vessel.
 13. The glass base material manufacturingapparatus as claimed in claim 10, wherein said deformation reductionmechanism includes a deformation restriction unit, which restrictsdeformation of said reaction vessel.
 14. The glass base materialmanufacturing apparatus as claimed in claim 13, wherein said deformationrestriction unit is provided around a circumference of said reactionvessel.
 15. The glass base material manufacturing apparatus as claimedin claim 14, wherein a material of said deformation restriction unitcomprises carbon steel or stainless steel.
 16. The glass base materialmanufacturing apparatus as claimed in claim 13, wherein the material ofsaid deformation restriction unit comprises a steel pipe having a squarecross section.
 17. The glass base material manufacturing apparatus asclaimed in claim 10, wherein said reaction vessel includes a wall, thesurface of which has a continuous flexural shape, as said deformationreduction mechanism.
 18. The glass base material manufacturing apparatusas claimed in claim 10, wherein said reaction vessel includes a slidepart, in which a part of a wall of said reaction vessel slides to beoverlapped with another part of said wall of said reaction vessel, assaid deformation reduction mechanism.
 19. The glass base materialmanufacturing apparatus as claimed in claim 18, wherein said slide partis formed around a circumference of said reaction vessel.
 20. The glassbase material manufacturing apparatus as claimed in claim 1, furthercomprising: a holding unit, which holds said deposit and transports saiddeposit outside the glass base material manufacturing apparatus, whereinsaid holding unit includes a means to hold a conical part, which isformed on both ends of said deposit.
 21. The glass base materialmanufacturing apparatus as claimed in claim 20, wherein said holdingunit includes a concave part, an angle of which is substantially same asan inclination of an angle of said conical part of said deposit.
 22. Theglass base material manufacturing apparatus as claimed in claim 21,wherein said concave part comprises a curved groove.
 23. The glass basematerial manufacturing apparatus as claimed in claim 21, wherein saidconcave part comprises a substantially V-shaped groove.
 24. The glassbase material manufacturing apparatus as claimed in claim 21, whereinsaid holding unit includes a clamp, which includes a concave part thatholds said conical part by sandwiching said conical part from both anupper side and a lower side of said conical part.
 25. The glass basematerial manufacturing apparatus as claimed in claim 24, wherein saidplurality of clamps are rotated around an axis, which couples saidplurality of clamps with each other.
 26. The glass base materialmanufacturing apparatus as claimed in claim 21, wherein said holdingunit comprises: a clamp including said concave part, which holds saidconical part by sandwiching said conical part; and a holding angleadjustment unit for adjusting an angle of said concave part of saidclamp to be substantially same as an angle of an inclination of a partof said conical part.
 27. The glass base material manufacturingapparatus as claimed in claim 26, wherein said holding angle adjustmentunit rotates said clamp around a longitudinal direction of said clamp asan axis.
 28. The glass base material manufacturing apparatus as claimedin claim 20, wherein said holding unit includes a holding pressureadjustment unit for holding said conical part by substantially uniformpressure.
 29. The glass base material manufacturing apparatus as claimedin claim 28, wherein said holding pressure adjustment unit comprises anelastic body formed on a surface of said clamp that contacts with saidconical part.
 30. The glass base material manufacturing apparatus asclaimed in claim 28, wherein said holding pressure adjustment unitincludes a plurality of columnar objects each of which movestelescopically according to a curved surface of said conical part. 31.The glass base material manufacturing apparatus as claimed in claim 24,wherein said holding unit includes a mechanism for adjusting a positionof said clamp in an axial direction of said deposit.
 32. The glass basematerial manufacturing apparatus as claimed in claim 31, wherein saidmechanism for adjusting said position of said clamp includes an arm thatsupports said clamp and screw shaft which engages with said arm andmoves said arm in the axial direction of said deposit.
 33. The glassbase material manufacturing apparatus as claimed in claim 9, whereinsaid second moving mechanism is provided on a lower part of the firstmoving mechanism, and wherein said second moving mechanism moves saidfirst moving mechanism reciprocatorily.
 34. The glass base materialmanufacturing apparatus as claimed in claim 9, wherein said first movingmechanism has a first moving axis arranged in parallel with thelongitudinal direction of the starting base material, and wherein saidsecond moving mechanism has a second moving axis arranged in parallelwith a longitudinal direction of said first moving axis.